With the continuous development of multimedia, the organic light emitting diode (OLED) display attracts great attention in the display market owing to its advantages such as a simple structure, an excellent operating temperature, a good contrast and a good view angle. The OLED displays are classified into passive matrix OLED displays and active matrix OLED displays. The active matrix OLED display is widely used because of its low power consumption. Reference is made to FIG. 1, which is a circuit diagram of a conventional pixel circuit in an organic light emitting diode display. The conventional pixel circuit has a 3T1C structure, that is, the conventional pixel circuit includes three P-type transistors and one capacitor. When the conventional pixel circuit operates, the transistor T3 transmits a reset voltage Vinit to an anode of the light emitting diode OLED under the control of a control signal S1, to reset the anode of the light emitting diode OLED. Then, the transistor T1 is turned on under the control of a signal supplied by a scan line, and a data voltage Vdata is supplied by a data line connected to the transistor T1. The data voltage Vdata is stored in the capacitor C, to ensuring the stability of the current to the light emitting diode OLED in one cycle. The transistor T2, which serves as a current driving transistor, is used to provide a current for the light emitting diode OLED to emit light.
However, since a threshold voltage of one transistor for driving the light emitting diode to emit light in a pixel circuit of a display device is different from that of transistors in other pixel circuits of the same display device depending on a manufacturing process, the light emitting diodes in the multiple pixel circuits may have different currents flowing therethrough when the multiple pixel circuits are supplied with the same data voltage, resulting in uneven light emission of the display device.